Abstract: Aiming at the problem that the impact toughness at room temperature of K4648 nickel-based superalloy for a certain type gas turbine guide could not meet the standard requirement (impact toughness greater than 20 J · cm⁻²), K4648 nickel-based superalloy was prepared at different casting temperatures and shell temperatures (1 490 ℃/1 050 ℃, 1 490 ℃/950 ℃, 1 460 ℃/1 050 ℃), and then the solid solution + standard heat treatment was carried out. The effects of casting temperature and shell temperature on the microstructure and impact properties of the alloy were studied, and the optimal process parameters were obtained. The results show that when the shell temperature or casting temperature was low, the grain size and the secondary dendrite spacing of the K4648 nickel-based superalloy, as well as the content and size of the primary bulk α-Cr phase were small. Meanwhile, the impact toughness of the alloy was large, and the number of secondary cracks at the impact fracture was small. The optimal process parameters were listed as follows: shell temperature of 950 ℃ and casting temperature of 1 490 ℃. The average impact toughness of K4648 nickel-based superalloy prepared under this process parameters was the highest, which was 21.4 J · cm⁻², meeting the standard requirement.